yes!
look at my 3rd live game
my bishop from e7 to d8.
I wanted to check the white king withj the bishop on e7. I than realized that i should loose the bshop after that move and decided to put it back on e7. it was moved accidentally onto d8 and i lost the game. terrible mouseslip.
Although what happened to me yesterday was a bit "tragic", it definitely is quite humorous as well! I was playing a 7 minute blitz game- and finally had trapped my opponent's king and forced him to sacrifice his rook to save mate. However, when I moved my pawn to capture his rook for free and gain a 5 point spread in material advantage- leaving him with one rook to my two in the endgame we were already in- I accidentally moved my pawn forward instead of diagonally capturing my opponent's rook! He captured the pawn, then proceeded to win the game that I previously had won, if I had not somehow slipped with my hand or mouse or whatever and blown the game!? Quite funny in retrospect! This makes me curious- does anyone else have stories about making such a funny but costly mistake in blitz chess- blowing a won game?:)